With the increased use of underground utilities, it has become more critical to locate and verify the placement of buried utilities before installation of additional underground utilities or before other excavation or digging work is performed. Conventional digging and excavation methods such as shovels, post hole diggers, powered excavators, and backhoes may be limited in their use in locating buried utilities as they may tend to cut, break, or otherwise damage the lines during use.
Devices have been previously developed to create holes in the ground to non-destructively expose underground utilities to view. One design uses high pressure air delivered through a tool to loosen soil and a vacuum system to vacuum away the dirt after it is loosened to form a hole. Another system uses high pressure water delivered by a tool to soften the soil and create a soil/water slurry mixture. The tool is connected with a vacuum system for vacuuming the slurry away into a collection tank. The tank may then be emptied by opening a door on the tank.
Prior art vacuum systems are provided with a tank having a manually closing door that is locked in a closed position by latches, locks or other suitable locking mechanisms. Such devices rely on an operator to apply the proper amount of force to ensure that a tight vacuum seal is created between an outer periphery of the door and the edge of the tank. However, if the locking force is applied at two opposing edges of the door or to a single point around the periphery of the door, then the closing force is greatest at the point where the door is locked closed. In an example where the locking points are positioned at 9 o'clock and 3 o'clock on the door, the greatest closing force occurs at 9 and 3 o'clock with the least closing force occurring at 12 and 6 o'clock. That is, as you move away from the locking points, the closing force on the periphery of the door begins to decrease. While a vacuum seal may be created, it cannot always be guaranteed especially if the door is warped.